Projects - Flex Builder - Using Local Style Definitations

.mxml code:
<?xml version="1.0" encoding="utf-8"?>
<mx:Application
xmlns:mx="http://www.adobe.com/2006/mxml"
width="150" height="140"
>
<mx:Style>
.solidBorder { border-style: solid; }

.solidBorderPaddedVertically
{
padding-top: 12;
padding-bottom: 12;
border-style: solid; }
</mx:Style>
<mx:VBox styleName="solidBorder">
<mx:Button label="Submit"/>
</mx:VBox>
<mx:VBox
styleName="solidBorderPaddedVertically"
>
<mx:Button label="Submit"/>
</mx:VBox>
</mx:Application>